[FFmpeg-trac] #10780(undetermined:new): Garbled output when doing colorspace conversion with zscale, since recent changes

[FFmpeg]

#10780: Garbled output when doing colorspace conversion with zscale, since recent
changes
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             Reporter:  Marth64      |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Description changed by Marth64:

Old description:

> **Summary of the bug:** Yesterday, a user on IRC #ffmpeg presented a
> sample image and said that when they were trying to re-encode it as a
> looping H265 video with some colorspace conversions, the output was
> garbled. The specific claim was that the resulting video was a half-black
> image, hiding most of the original source picture.
>
> I was able to help the user verify this behavior and confirmed it was a
> bug, at least had them to roll back to an older version where this
> behavior does not exist.
>
> This must have been recently introduced, since when I run from a build on
> 12-27 I was not able to reproduce the issue. So sometime between 12-27
> and 1-4, this bug was introduced.
>
> The user was kind enough to share the source image and give permission to
> post it here. Attached files:
> - colors2.exr - image from user
> - output(latest).mkv - buggy output
> - output(6.0.1).mkv - expected output
>
> **How to reproduce:**
> {{{
> ffmpeg -loop 1 -t 10 -i colors2.exr -filter:v
> 'zscale=rangein=full:primariesin=709:transferin=709:matrixin=709:range=full:primaries=2020:transfer=smpte2084:matrix=2020_ncl'
> -pix_fmt:0 yuv420p10 -colorspace:0 bt2020nc -color_primaries:0 bt2020
> -color_trc:0 smpte2084 -color_range:0 pc -c:v libx265 -x265-params
> lossless=1 OUTPUT.mkv
> }}}

New description:

 **Summary of the bug:** Yesterday, a user on IRC #ffmpeg presented a
 sample image and said that when they were trying to re-encode it as a
 looping H265 video with some colorspace conversions, the output was
 garbled. The specific claim was that the resulting video was a half-black
 image, hiding most of the original source picture, and that the dynamic
 color range is lost. I am focusing this ticket on the half-black image
 part of the issue since the output is not watchable.

 I was able to help the user verify this behavior and confirmed it was a
 bug, at least had them to roll back to an older version where this
 behavior does not exist.

 This must have been recently introduced, since when I run from a build on
 12-27 I was not able to reproduce the issue. So sometime between 12-27 and
 1-4, this bug was introduced.

 The user was kind enough to share the source image and give permission to
 post it here. Attached files:
 - colors2.exr - image from user
 - output(latest).mkv - buggy output
 - output(6.0.1).mkv - expected output

 **How to reproduce:**
 {{{
 ffmpeg -loop 1 -t 10 -i colors2.exr -filter:v
 'zscale=rangein=full:primariesin=709:transferin=709:matrixin=709:range=full:primaries=2020:transfer=smpte2084:matrix=2020_ncl'
 -pix_fmt:0 yuv420p10 -colorspace:0 bt2020nc -color_primaries:0 bt2020
 -color_trc:0 smpte2084 -color_range:0 pc -c:v libx265 -x265-params
 lossless=1 OUTPUT.mkv
 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/10780#comment:1>
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